Al Qaeda, an Arabic word meaning "the Base," was founded in approximately 1988 by Osama bin Laden, Abdullah Azzam, and Muhammad Atef -- the latter a native Egyptian and a onetime member of the terrorist group Egyptian Islamic Jihad. Al Qaeda grew out of the Services Office, a clearinghouse for the international Muslim brigade that opposed the 1979 Soviet invasion of Afghanistan. In the 1980s, under the leadership of bin Laden and the Palestinian religious scholar Abdullah Azzam, the Services Office recruited, trained, and financed thousands of foreign mujahideen, or "holy warriors," from more than fifty countries. Seeking to extend the Islamic jihad, or "holy war," beyond the borders of Afghanistan even after the March 1988 Soviet pledge to withdraw its forces, bin Laden created al Qaeda. Over the years, the organization has supported Muslim fighters in Afghanistan, Bosnia, Chechnya, Tajikistan, Somalia, Yemen, Iraq, and Kosovo. It also has trained members of terrorist organizations from the Philippines, Algeria, and Eritrea.

To prepare his recruits to wage jihad, bin Laden established training camps in various places, including Afghanistan, Pakistan, Somalia, Kenya, and Sudan. He also set up a series of businesses - including two investment companies, an agricultural company, a construction business, and a transportation company - to generate income for al Qaeda and to provide cover for the group's activities.

The U.S. government characterizes al Qaeda, whose worldwide presence in the mid-2000s consisted of at least several thousand members and associates from perhaps 100 countries, as "an international terrorist group . . . dedicated to opposing non-Islamic governments with force and violence." Law enforcement has broken up al Qaeda cells in the United Kingdom, the United States, Italy, France, Spain, Germany, Albania, Uganda, and elsewhere.

Bin Laden remained the official leader of al Qaeda until his death in 2011, at which time his top lieutenant and ideological adviser, Ayman al-Zawahiri, took control of the group. Another key al Qaeda figure was the late Jordanian radical Abu Musab al-Zarqawi, who directed a series of deadly terror attacks and videotaped beheadings in Iraq, where he headed al Qaeda's resistance operations against the American military during the Iraq War.

Numerous senior al-Qaeda officials have been captured or killed since 9/11. Co-founder Muhammad Atef, for instance, was killed by a November 16, 2001 U.S. air strike on his home near Kabul. Another top lieutenant, Abu Zubaydah, was captured in Pakistan in March 2002. A year later, the alleged mastermind of the September 11 attacks, Khalid Sheikh Mohammed, was captured in Pakistan along with al Qaeda treasurer Mustafa Ahmed al-Hawsawi.

It is common for senior al Qaeda leaders to serve also as senior leaders in other terrorist groups such as Egyptian Islamic Jihad (with which al Qaeda formally merged in June 2001) and the Egyptian al-Gama'at al-Islamiyya (a.k.a. the Islamic Group, which was formerly led by Sheik Omar Abdel Rahman, the mastermind of the 1993 World Trade Center bombing and numerous other murderous plots). According to the U.S. government, "Al Qaeda also forged alliances with the National Islamic Front in Sudan and with representatives of the government of Iran and its associated terrorist group Hezbollah for the purpose of working together against their perceived common enemies in the West, particularly the United States." Other terrorist organizations with ties to al Qaeda include the Libyan Islamic Fighting Group; the Islamic Army of Aden (Yemen); Jama'at al-Tawhid wal Jihad (Iraq); Lashkar-e-Taiba (Kashmir); Jaish-e-Muhammad (Kashmir); the Islamic Movement of Uzbekistan; the Salafist Group for Call and Combat (Algeria); the Armed Islamic Group (Algeria); Abu Sayyaf Group (Malaysia, Philippines); and Jemaah Islamiya (Southeast Asia). These groups share al-Qaeda's Sunni Muslim fundamentalist views.

By fomenting the global radicalization of Islam, al Qaeda's overriding objective is to establish a worldwide caliphate governing the entire world via the dictates of Islamic Law, or Sharia. A task crucial to the achievement of that goal is the destruction of America by any means necessary. The organization's worldview and ideals are spelled out clearly in a 1998 document titled "Jihad Against Jews and Crusaders," which bin Laden co-authored with, among others, Ayman al-Zawahiri. This document accused Americans of having made "a clear declaration of war on God, his messenger, and Muslims." "On that basis," bin Laden and Zawahiri reasoned, "and in compliance with God's order, we issue the following fatwah [ruling on Islamic law] to all Muslims: The ruling to kill the Americans and their allies -- civilians and military -- is an individual duty for every Muslim who can do it in any country in which it is possible to do it . . . to comply with God's order to kill the Americans and plunder their money wherever and whenever they find it. We also call on Muslim ulema, leaders, youths, and soldiers to launch the raid on Satan's U.S. troops and the devil's supporters allying with them, and to displace those who are behind them so that they may learn a lesson."

In a June 2002 manifesto (translated by the Middle East Media Research Institute), al Qaeda spokesman Suleiman Abu Gheith wrote, "America is the head of heresy in our modern world, and it leads an infidel democratic regime that is based upon separation of religion and state and on ruling the people by the people via legislating laws that contradict the way of Allah and permit what Allah has prohibited. . . . America is the reason for all oppression, injustice, licentiousness, or suppression that is the Muslims' lot. . . . We have the right to kill 4 million Americans - 2 million of them children - and to exile twice as many and wound and cripple hundreds of thousands. Furthermore, it is our right to fight them with chemical and biological weapons. . . . America is kept at bay by blood alone."

Al Qaeda's objectives, motives, and strategies are further detailed in an Al Qaeda Training Manual designed to instruct aspiring terrorists in the art of murdering "infidels." The manual was discovered by England's Manchester Metropolitan Police during a search of an al Qaeda member's home. "Islamic governments have never and will never be established through peaceful solutions and cooperative councils," states this publication. "They are established as they [always] have been by pen and gun, by word and bullet, by tongue and teeth." The manual further exhortsjihadists to "pledge . . . to make their [the infidels'] women widows and their children orphans . . . to slaughter them like lambs and let the Nile, al-Asi, and Euphrates rivers flow with their blood . . . to be a pick of destruction for every godless and apostate regime."

In addition, the manual enumerates what it calls "Missions Required of the Military Organization." Among these are: "Assassinating enemy personnel as well as foreign tourists; . . . Spreading rumors and writing statements that instigate people against the enemy; Blasting and destroying the places of amusement, immorality, and sin; Blasting and destroying the embassies and attacking vital economic centers; Blasting and destroying bridges leading into and out of the cities."

Finally, the manual explicitly declares that among al Qaeda's "long-term goals" is "the establishment of an Islamic state." But an "Islamic government would never be established except by the bomb and rifle," the manual informs. "Islam does not coincide or make a truce with unbelief, but rather confronts it. The confrontation that Islam calls for with these godless and apostate regimes, does not know Socratic debates, Platonic ideals nor Aristotelian diplomacy. But it knows the dialogue of bullets, the ideals of assassination, bombing, and destruction, and the diplomacy of the cannon and machine-gun."

Opposed to the presence of any Westerners or non-Muslims in the Arab world, Osama bin Laden issued numerous fatwahs stating that American forces stationed in Saudi Arabia, Yemen, and the Horn of Africa (including Somalia), should be attacked. In response to the latter directive, al Qaeda members provided military training to Somali tribes opposed to the United Nations' intervention in Somalia during the early 1990s. In October, 1993, in Mogadishu, al Qaeda-trained operatives ambushed American military personnel who were serving in the region as part of Operation Restore Hope; this attack resulted in the killing of 18 U.S. soldiers.

Over the years, al Qaeda has been linked to a host of terrorist and assassination plots -- some successful, others not. Among its foiled enterprises were plans to assassinate Pope John Paul II during his visit to Manila in late 1994; to kill President Bill Clinton during a visit to the Philippines in early 1995; to bomb in midair a dozen U.S. trans-Pacific flights in 1995; to set off a bomb at Los Angeles International Airport in 1999; to carry out terrorist attacks against American and Israeli tourists visiting Jordan in 1999; to ignite a shoe bomb on a transatlantic flight from Paris to Miami (the aspiring perpetrator was al Qaeda operative Richard Colvin Reid); and to shoot down an Israeli chartered plane with a surface-to-air missile as it departed the Mombasa airport in November 2002.

Among al Qaeda's successful terrorist attacks were the August 1998 bombings of U.S. embassies in Kenya and Tanzania (killing a combined total of 301 people and injuring more than 5,000 others); the October 12, 2000 attack on the USS Cole in Yemen, killing 17 U.S. Navy members and injuring another 39; the September 11, 2001 multiple airliner hijackings that resulted in nearly 3,000 deaths in New York City, the District of Columbia, and Pennsylvania; the April 11, 2002 firebombing of a Tunisian synagogue that killed 19 and injured 22; the October 6, 2002 suicide attack on the MV Limburg off the coast of Yemen that killed one and injured four; an October 8, 2002 attack on U.S. military personnel in Kuwait, which killed American soldier; an October 12, 2002 nightclub bombing in Bali, Indonesia that killed approximately 180; a November 28, 2002 hotel bombing in Mombasa, Kenya that killed 15 and injured 40; a May 12, 2003 bombing of three expatriate housing complexes in Riyadh, Saudi Arabia that killed 20 and injured 139; the May 16, 2003 bombings of a Casablanca, Morocco Jewish center, restaurant, nightclub, and hotel that killed 41 and injured 101; the August 5, 2003 bombing of the J.W. Marriott Hotel in Jakarta, Indonesia that killed 17 and injured 137; the November 9, 2003 bombing of a Riyadh housing complex that killed 17 and injured 100; the November 15, 2003 bombings of two Turkish synagogues that killed 23 and injured 200; the November 20, 2003 Istanbul bombings of the British Consulate and HSBC Bank which left 27 dead and 455 injured; and the March 2004 bomb attacks on Madrid commuter trains, which killed nearly 200 people and left more than 1,800 injured.

In August 2007, Vice Admiral (ret.) John Scott Redd, head of the U.S. government's National Counterterrorism Center, toldNewsweek that al Qaeda had an active plot to hit the West, and that the United States was aware of it but did not possess enough tactical detail to issue a precise warning or to raise the threat level.

In November 2010, al Qaeda announced that it had launched "Operation Hemorrhage," an initiative whose goal was to target the West not with spectacular attacks like 9/11, but rather "with smaller but more frequent operations ... what some may refer to as the strategy of a thousand cuts." "The aim," said al Qaeda, "is to bleed the enemy to death." This announcement came in the aftermath of an October 2010 mission where al Qaeda operatives had planted printer bombs aboard two cargo flights at a cost of only $4,200. That plot, which failed when the explosives-laced printer cartridges were discovered before detonating by authories in Britain and Dubai, was not meant to kill more than the pilot and co-pilot of each plane. The larger goal, however, was to force the U.S. government to spend billions of dollars on preventive security screening measures thereafter.

Late on the night of May 1, 2011, forty U.S. Navy SEALS raided the Pakistani home which had been determined to be the hiding place of Osama bin Laden. They found bin Laden therein and fatally shot him.

Bin Laden's death marked the start of a period of decline in al Qaeda's power and influence.

On June 16, 2011 -- a few weeks after the death of bin Laden -- al Qaeda announced that Ayman al-Zawahiri would be its new leader. The organization released a statement that said: “As the best form of gratitude for the righteous martyr and for the life of the mujahid Sheikh Osama bin Laden is to continue on the path of jihad . . . the General Command of Qaeda . . . announces that Sheikh Dr. Abu Muhammad Ayman al-Zawahiri . . . has assumed the responsibility of the leadership the group.”

On August 27, 2011, U.S. officials announced that al-Qaeda’s second-in-command, Atiyah Abd al-Rahman, had been killed by an American missile strike five days earlier in the lawless Pakistani tribal region of Waziristan.

In June 2015, two of al Qaeda's spiritual leaders, Abu Qatada and Abu Muhammad al-Maqdisi, said that their group was rapidly losing money and manpower due to the dramatic rise of the powerful Islamic State terror group (a.k.a. ISIS, or ISIL). According to Maqdisi, al Qaeda leader Ayman Al-Zawahiri was isolated from his top lieutenants and "operates solely based on the allegiance." "There is no organizational structure," Maqdisi added. "There is only communication channels, and loyalty." Meanwhile, a former al Qaeda member-turned-British intelligence agent said that at one point in 2014 the group was in such bad shape financially, that it had to sell many of its laptop computers and motor vehicles in order to raise money for necessities like food and rent.